1. Field of the Invention
The method of this invention relates to a method for measuring skin erythema. The method of this invention utilizes digital image analysis of conventional photos that can be acquired by inexpensive digital cameras. This method is useful for demonstrating the efficacy of skin care products intended for the prevention and/or reduction of erythema, even when such erythema is not apparent to the naked eye.
2. Description of the Prior Art
Skin inflammation is often manifested as skin redness (erythema). Erythema is frequently associated with diaper rash, acne, dermatitis, eczema and other skin conditions. Many skin care products are designed either to prevent inflammation, as in the case of sunscreens, or to reduce imflammation, as in the case of diaper rash ointments). Significant skin inflammation may be present even after use of such skin care products but may not be apparent to the naked eye. While in many cases, individuals suffering from such inflammation can report that the inflammation and irritation is still present after use of such products, infants or others who are not able to express themselves, can continue to endure symptoms despite treatment. There is, therefore, a need for a method that is capable of demonstrating the efficacy of such skin care products more accurately.
Skin erythema is primarily due to vasodilation and local increases in hemoglobin concentration. The hemoglobin concentration in skin can be evaluated using several methods.
Chromameters have been utilized for analyzing hemoglobin. Chromameters give values of standardized parameters for color evaluation: L*,a*,b*, with a* being used as an indicator of the “red” content and therefore related to skin erythema.
Spectrophotometers have been used in a method for analyzing hemoglobin based on diffuse reflectance spectroscopy, according to which the reflected light from skin is collected and analyzed into its spectral components. Spectral analysis algorithms have been used to calculate chromophore concentrations including oxy- and deoxy-hemoglobin (relating to erythema). Various light reflectance devices such as a Mexameter are also known for giving an erythema index.
Spectral imaging is a method that combines the spectral information with two-dimensional spatial information to calculate intensity maps corresponding to chromophore concentrations including oxy- and deoxy-hemoglobin. The analysis of digital color images of skin has also been utilized for analyzing hemoglobin.
All of the methods described above have deficiencies in their ability to measure inflammation to the degree required in order to ensure treatment of a skin condition causing inflammation. Reflectance-based methods only give point measurements and are limited by the size of the probe used in conjunction with the method. Spectral imaging is the most accurate method for mapping hemoglobin concentration but requires specialized and expensive equipment. Methods using digital image analysis do not take into appropriate consideration all optical parameters of the skin that contribute to the perception of erythema. Therefore, there is a continuing need for a method for measuring skin erythema.